Autism Spectrum Disorders

Autism spectrum disorders (ASDs) are a group of complex neurodevelopmental disorders that generally appear in the first three years of life. ASDs are characterized by deficits in social and language skills, as well as repetitive interests or behaviors. Symptoms of ASDs may be mild or severe.

Studies have found that children with an ASD often have abnormalities in their brain biology and chemistry. Imaging research indicates that autism involves a failure to develop normal connections between regions of the cerebral cortex, an outer layer of the brain where the bodies of the neurons reside. After a period of normal growth, neural circuitry in the cortex begins to lag behind the normal growth pattern, leading to a brain that may lack crucial connections between regions of the cortex. This may account for some of the language, social skills and behavior deficits seen in autism.

Despite these challenges, people with autism often have more activity in the back of the brain, in regions typically used for visual and spatial perception, and may use these regions to compensate for differences elsewhere in the brain.

In most cases, the cause of autism is unknown. Experts believe that ASDs are likely caused by an interaction between genes and external factors, such as prenatal and environmental conditions.

Behavioral, medical, and possibly computer-based treatments can help children with autism learn and minimize symptoms.

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Causes of Autism

Genetic Causes

Autism is one of the most heritable psychiatric illnesses, with identical twins having up to a 90 percent chance of sharing the diagnosis. About 100 autism-linked genes have been discovered so far, most of them overlapping with other disorders such as epilepsy and ADHD.

Despite mounting evidence for its genetic origins, autism cannot be explained by a single gene or even a dozen genes. Experts do not know precisely how many genes are involved, or how genetic factors interact with environmental ones to predispose a child to autism.

Some have suggested that the autism spectrum is not a single disease with a single genetic cause, but a collection of rare disorders caused by several different genetic variations.

Environmental and Epigenetic Causes

In the past, many scientists were skeptical of non-genetic explanations for autism. However, it is now becoming clear that ASDs result from an interaction between genes and other factors, such as prenatal and environmental conditions.

No toxin has been shown to single-handedly cause autism, but environmental conditions may affect children with some genes more than others. The conditions guiding the expression of genes within a cell, known as epigenetics, may also help explain why autism emerges. Some researchers have suggested that the genes of an autistic child may not be altered at all, but simply expressed differently.

Disproven Causes

Despite the uncertainty about the causes of autism, two often-cited causes have been definitively ruled out. First, mercury in childhood vaccinations do not cause autism. Population studies have found no evidence for a connection between vaccination and autism. Mercury was removed from vaccines in California more than a decade ago, yet the state's autism rates have continued to rise.

Second, autism is not caused by bad parenting. When the disorder was first identified in the U.S. in the 1950s, some conjectured that children with autism were guarding themselves against the rejection of a "refrigerator mother." This view proved mistaken. Autism has many causes, but absence of sufficient love is not one of them.

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Early indicators that a baby might be on the autism spectrum include a lack of pointing and talking, an absence of interest in games, and a sense of withdrawal or unresponsiveness.

A baby who shows a few of these signs doesn't necessarily have autism. An 18-month-old who hasn't begun to talk could be autistic, or he or she might have trouble hearing, be under-stimulated or just slower to develop language.

Autism involves impairment in three distinct areas of development. The first is social skills. Young children with autism have limited eye contact, facial expressiveness and body language. They don't seek the attention of parents in the usual way and become cut off from social learning.

The second area of impairment is language. Children with autism speak mainly to get their needs met and rarely to have conversations, or they simply do not talk much at all. They may also have trouble engaging in make-believe and even simple physical play with peers.

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ASDs may go undiagnosed, especially if the symptoms are mild or if they are masked by another, more severe disorder.

Health care providers often use screening questionnaires to evaluate children's development and behavior. If the screening suggests the possibility of an ASD, a more comprehensive evaluation from an autism specialist or team of specialists — which may include a developmental pediatrician, neurologist, psychiatrist, psychologist or other professionals who diagnose ASD — may be appropriate.

The evaluation will include a thorough neurological assessment and cognitive and language testing. Because hearing disorders cause symptoms that may be mistaken for an ASD, children should also undergo a hearing test.

Early, intensive treatment can often help children with learning and behavior issues. Treatment plans should be tailored to the individual needs of the child. Parents should work with a specialist or team of specialists to design a program that is most likely to benefit their child.

Treatment may include medications to help with behavior problems such as inattention or aggression. However, medications should always be used along with — not in place of — behavioral treatments.

Behavioral Treatments

Most typically-developing children learn as a result of natural curiosity and desire for parental praise. When these are absent in children with autism, normal behavior and learning are derailed.

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UCSF Research & Clinical Trials

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Reviewed by health care specialists at UCSF Benioff Children's Hospital.